1. Field of the Invention
The invention relates to a light source and a display device, and more particularly, the invention relates to a light emitting diode (LED) package and a projection apparatus.
2. Description of Related Art
Since luminescence efficiency of a light emitting diode (LED) has been increasing in recent years, the LED is gradually replacing traditional light source in many fields. Since the luminance of the LED is not caused by thermal emission or electric discharge but by cold luminance, the life span of the LED may be more than 100,000 hours. In addition, LEDs also have advantages of high responsive speed (about 10−9 seconds), small size, low power consumption, little pollution, high reliability, being adapted for mass production and so on. Accordingly, LEDs are wildly used in many fields.
In general, the light intensity emitted by LED chips is presented as lambertian intensity distribution. That is, a certain degree of light intensity also exists in the direction deviated from the optical axis of an LED chip. Thus, when LEDs are used as the light source of a projection apparatus, the directivity of light emitted by LEDs usually needs to be increased by light condensing components. A prior art arranges a light integration rod directly in front of LED chips to collect the light emitted by LED chips. When an LED chip adopts wire bonding techniques and is electrically connected to a circuit substrate by bonding wires, an interval has to be kept between the light incident end of the light integration rod and the light emission surface of the LED chip, so as to avoid interference of the light integration rod and bonding wires. However, on the other hand, if the light integration rod is too far away from the light emission surface of the LED chip, an excessive percentage of the light off the optic axis may not enter the light integration rod, resulting in too much light loss. Therefore, proper control of the distance between the light integration rod and the LED chip becomes a decisive factor to the improvement of light efficiency.
Nevertheless, since the size of an LED chip is smaller than other light emitting devices such as ultra high pressure (UHP) lamps, the volume of a light integration rod adapted to the LED chip has to shrink accordingly. As a result, it is difficult to align the light integration rod and LED chip, and thus the alignment error is too large and the alignment time is too long. Moreover, the large alignment error causes the yield to decrease and the long alignment time is disadvantageous to mass production.